A common network architecture utilizes a host device that has access to multiple network egress points. This architecture may be utilized in wired, wireless and hybrid networks.
FIG. 1 illustrates such an architecture in which hosts A, B, C, D, E, F, and G connect via a shared medium with egress device 1 220, egress device 2 222, and egress device 3 224. Each host may have logical links to different egress devices. As illustrated in FIG. 1, hosts A, B, C and D are linked to egress device 1 220. Hosts C, D and E are linked to egress device 2 222. Hosts B, C, F and G are linked to egress device 3 224. The egress devices 220, 222, and 224 provide a physical and logical connection to a network 200.
The actual physical connection of host and an egress device may involve any number of network devices. For example, a host may connect to one or more hubs and/or switches (represented in FIG. 1 by the shared medium). Other devices may be interposed between the host and an egress device and between an egress device and the network 200.
FIG. 2 illustrates another common architecture in which the multi-paths are provided over different shared media thereby providing for redundancy and failover protection. As illustrated in FIG. 2, hosts A, B, C and D are linked to egress device 1 220 via shared medium 230. Hosts C, D and E are linked to egress device 2 222 via shared medium 232. Hosts B, C, F and G are linked to egress device 3 224 via shared medium 234.
A host may detect the status of its physical link (i.e., whether it is physically/electrically connected, or not). A physical interface of a host may be lost due to a failure or disconnection of a cable or the failure of a switch or hub to which the physical link is connected.
A host may also check the efficacy of a logical path by sending probes. A probe confirms that the host is able to communicate by sending messages to a number of devices in the path. As long as these devices respond to the probe, a logical link is considered operational. When the devices do not react in a certain time, the link is considered as failed and the host will attempt to roll-over to a different path.
Referring to FIGS. 1 and 2, the hosts A-G may randomly test their data paths to egress devices to which they are connected using probe messages. The probe messages travel over the same paths as other data. The probe messages are not coordinated. As a consequence, bandwidth and processing that would otherwise be available for data communications are consumed to respond to the continuous stream of probe messages. More hosts mean more probe messages and further network degradation. In addition, the probing messages may cause the static or default route device to become unstable due to delays in servicing the tests instead of servicing their original intended function (routing traffic).